1. Field of the Invention
This invention relates to a method for the production of a succinimide type polymer and an aspartic acid type polymer.
2. Description of the Related Art:
A succinimide type polymer, when hydrolyzed, gives rise to a corresponding succinimide type polymers which are useful as detergent additives, dispersion stabilizers, scale preventing agents, humectants, and fertilizers.
As means to obtain polysuccinimide by thermal polymerization of aspartic acid as the raw material, various methods have been heretofore proposed.
German Patent publication DE4429108 A1 discloses a method for effecting polymerization of aspartic acid by vacuum concentrating the ammonium salt solution of aspartic acid and further heating the resultant concentrate.
According to this method, the yield of polysuccinimide is 30% when the polymerization temperature is 180.degree. C. and the polymerization time is 4 hours. To heighten the polymer yield, this method requires the polymerization temperature to rise to 220.degree. C. Further, the polyaspartic acid that has been obtained by this method has the problem of deficiency in biodegradability.
EP 0 705 794 A2 discloses a method for polymerizing aspartic acid in the presence of an acid catalyst. This method uses an acid form aspartic acid as the raw material. Since aspartic acid is generally produced in the form of a solution, the method requires separating the acid form aspartic acid in advance from the solution prior to the actual use of the aspartic acid. This extra treatment of separation has formed a cause for heightening the cost of production.